1. Field of the Invention
The present invention relates to a raisable-lowerable member for a crane, including a boom.
2. Description of the Background Art
A conventional crane comprises: an upper slewing body constituting a crane main body; a boom pivot turnably attached to the upper slewing body so as to be able to be raised and lowered; and a mast attached to the upper slewing body pivot turnably about an axis parallel to a pivot-turn-axis of the boom, wherein a distal end of the boom and a distal end of the mast are joined together via a guy line to turn the boom in a raising-lowering direction in interlocking relation with the turning of the mast, as disclosed, for example, JP 2010-195542A (hereinafter referred to as “Patent Document 1”) and JP 2010-18355A (hereinafter referred to as “Patent Document 2”).
In this type of crane, during disassembling of the crane for transportation, there can be a case of not only detaching the upper slewing body and the boom from each other but also detaching the upper slewing body and the mast from each other. For example, in a situation where leaving the upper slewing body and the mast mutually mounted to each other prevents them from avoiding a problem of exceeding a size limit or a weight limit during transportation on public roads, the upper slewing body and the mast have to be detached from each other. In this case, re-assembling the crane after the transportation requires re-attaching of the upper slewing body and the mast together. Thus detaching and re-attaching the upper slewing body and the mast are not easy, involving a problem of taking a lot of time for operations for assembling and disassembling of the crane.